Sound apparatus



y 1934. R. L. WILLIAMS 1,960,257

SOUND APPARATUS Original Filed May 23. 1929 I ATTORA/f) Patented May 29,1934 UNITED STATES PATENT OFFICE 1,960,257 SOUND APPARATUS RobertLongfellow Williams, Newton, Mass., as-

signor to Submarine Signal Company, Boston, Mass., a corporation ofMaine 4 Claims. (Cl. 177-7) This application is a division of myapplication Serial No. 365,385, filed May 23, 1929.

The present invention relates to means for creating sound waves in anymedium, but more particularly in air.

There are many types of sound'generators. For fog or bad weathersignaling, it has been common practice to use air sirens, steam or airwhistles. A newer type of sound'producer for fog signaling is theelectromagnetic and electrodynamic type, sometimes called airoscillators.

These air oscillators are usually designedto produce a sound of a puretone and are found to carry further distances on account of the purenote which they produce. This is due, it is believed, to the fact thatin the propagation of a pure tone, the phases do not become mixed, sothat there is less wattless energy oscillating back and forth in themedium. Besides this, the ear very readily detects a pure tone, eventhough it is weak, because of its accumulative effect in building up asubstantial vibration.

It is desirable, therefore, to have a pure tone, and for that reason theair oscillators have been given a definite oscillating. resonantfrequency and have been operated at that resonant frequency.

Air oscillators are operated by alternating current sources deliveringpower at the frequency at which the sound is to be generated. While thegenerators remain at the frequency at which the sound is to be produced,the maximum energy may be drawn from the electric system, but when thefrequency of the electric system falls 01f resonance, as when a changein voltage occurs or when other changes take place, the maximum amountof energy cannot be absorbed and radiated by the air oscillator.

The temporary variations causing temporary fluctuations of the poweremitted by air oscillators is not very serious, but when the variationsare more than temporary, the power output of the air oscillators may beconsiderably diminished and. consequently its range of audibility may beaffected. This difficulty may be overcome either by having a systemwhich has 'no particular resonance or by having a system in which theresonance may be controlled, or by a combination of the two methods.

Where the system has no marked resonance, it has been found difficult insome cases to produce great enough amplitudes to radiate the powerdesired with the size of radiator available for use. To overcome thisobjection without the introduction of a tuned system, I employ a leverarrangement whereby the amplitude of the electrical system is multipliedat the sound radiating element.

To increase further the power radiated, the radiating member may beloaded by putting a horn or an adjustable resonating chamber before it.The horn, while having some resonant characteristics, is not sharplymarked and the adjustable resonant chamber being adjustable within therange which the frequency may vary, the system as a whole can readily bemade to radiate at its maximum output and allow reception of the soundsignal at uniform distances practically all the time.

The invention will be best understood from a consideration of thefollowing description and drawing in which Figure 1 shows a section ofmy invention;

Figures 2 and 3 show details of Figure 1; and

Figure 4 shows a modification of a detail in Figure 1.

In Figure 1 the electrical system is of the Fessenden oscillator type asshown in the Fessenden Patent No. 1,167,366. Here the system comprises acore 3, an outer shell 1 composed of two parts bolted together at theflange 5 by bolts 6. Within the shell 1 is a coil 2 in which directcurrent flows to magnetize the air gap between the core 3 and theshell 1. Wound upon the core 3 is a winding 7, through which thealternating current flows for producing alternating current in thecopper or aluminum tube 8. The change of current in the tube 8 causes itto move back and forth longitudinally in the air gap and impart soundvibrations to the sound radiating element.

The system shown produces motion both Ways and therefore needs nosprings or restoring forces, as in some systems, to bring theoscillating elements back to their starting or normal positions.

The central core 3 is held in position by cars or corners 9, 9, 9, 9 tothe outer shell 1. Mounted on these ears are bearing pieces 10, forkedin shape as shown in Figure 3. These pieces support the levers 11 attheir ends by the pins 12 which pass through the levers and the bearingpieces. The levers 11 have their other ends resting in a groove 13 inthe collar piece 14. The levers 11 are spaced radially from the centralcollar piece 14, as shown in Figure 2, where there are three in number.There may be more or less, in accordance with the most suitable design.The center collar 14 carries the spider 15, to which the radiatingelement 16 is attached.

The top of the shell 1 is closed by the horn element 17 in the throat ofwhich the radiating piston 16 works. Closing the edge between theradiating piston and the horn is a disc of rubber or other suitablematerial 18, clamped to the member 16 and to the Wall for preventing thepressure release to the back of the radiating element and also toprotect the inside mechanism from moisture and bad weather.

At the lower end of the oscillator are pr vided similar levers 11mounted and fastened, in the same manner as the levers at the top exceptthat there is no radiating member attached to the collar 14. vAradiating member may be used here, however, if it is desired to radiatefrom both ends.

The copper tube 8, which may be of some other suitable conductingmaterial if desired, has projecting arms 19 which may have knifed edgeends 20 fitting into cuts in the levers 11 near the pivoted ends, asshown in Figure 1.

When the system is assembled, the various elements are put together andthe nuts 21, 21 at opposite ends of the rod 22 are tightened until thedesired pressure is exertedbetween the levers 11 and the arm 19extending from the copper tube. This also tensions the levers 11 againstthe bearing support 12 so that the system is a unified structure.

The tube 8 and the arms '19 have only a small motion, but at the freeend of the levers 11, at the collar 14, the motion is multiplied in. theratio of the length of the lever to the distance between the point ofbearing of the arm 19 and the pointof pivot. The center collar has,therefore, an increased amplitude which is imparted to the radiatingelement 16 through the spider 15.

The system as shown in Figure 1 has no marked resonance so that if thefrequency of the alternating current impressed upon the coil '7 shouldchange, due to change in the frequency Having now described myinvention, I claim:

1. A means for producing sound waves comprising an electricallyoscillated shell element, a. plurality of levers positioned at oppositeends of said shell and extending from a position outside of the shellelement towards the shell center, means pivoting the outer extremitiesof said levers adjacent opposite ends of the shell, means for connectingthe inner ends of said levers and exerting a pressure between the leverspositioned at opposite ends of the shell, a sound radiating element andmeans connecting said sound radiating element with the inner ends ofsaid levers and means for oscillating said shell element.

2. A means for' producing sound waves comprising an electrodynamicoscillating mechanism including a cylindrical moving element, aplurality of levers, means for fixing and supporting said levers,'atopposite ends of said cylindrical element and means cooperating withsaid levers for firmly supporting said cylindrical element between saidlevers, including means forming a part of said cylindrical element andprojecting to said levers, and a radiating element attached to the meanscooperating with said levers.

3. A means for producing sound waves comprising an electrodynamicoscillating mechanism, including an enclosed moving element, a pluralityof levers, means for fixing and supporting one set of ends of the leversexternally adjacent to opposite ends of said moving element and bearingon the same at points near the lever supporting means, and means holdingthe other ends of the opposite groups of levers together to exertpressure on the bearing points between the levers and the movingelement, and radiating means attached to said last named means.

4. A means for producing sound waves comprising an electricaloscillating mechanism including an enclosed moving element, a pluralityof levers, means for fixing and supporting one set of ends of the leversexternally adjacent to opposite ends of said moving element and bearingon the same at points near the lever supporting means, and means holdingthe other ends of the opposite groups of levers together to exertpressure on the bearing surfaces between the levers and the movingelement, and a radiating means attached to the point of greatest motionof the moving system.

ROBERT LONGFELLOW WILLIAMS.

